A continuous washing path has been employed for laundering large quantities of items. Generally these items are passed through the washing machine in a direction opposite to the flow of washing or rinsing liquid and especially in the washing process to facilitate economical water and energy consumption.
The elongated washing trommel or drum is rotated about its longitudinal axis and is subdivided axially into a number of washing chambers or compartments and into a plurality of washing zones each formed by a plurality of adjacent washing chambers.
For example a single counterflow cycling washing machine drum of this type often may be divided into an initial soaking zone having two or more compartments, a true washing zone having the largest number of compartments, and a rinsing zone which can have fewer compartments than the washing zone.
The items to be washed are fed to a loading washing chamber and thereafter are transferred in discrete batches from one chamber to another through the individual washing chambers and zones according to a cyclic process. Specifically, the drum may angularly oscillate about its axis to a certain extent to agitate each batch in the respective chamber in a corresponding treatment liquid and in accordance with the desired washing cycle. Then a further rotation of the drum will automatically transfer the batches in a direction of movement into the next compartment (see Re. Pat. No. 30,214 and U.S. Pat. No. 4,020,659).
Toward the end of the wash trommel which is downstream with respect to the movement of wash, fresh water is supplied which at least partialy flows through the washing trommel in counterflow to the laundered articles. These processes are problem free as long as only white pieces of wash are washed in such a unit.
The proportion of pigmented wash, for example green or blue wash, colored bedding, table cloths or napkins is currently very large and is expected to grow further. However when brightly colored and white wash materials are laundered together in a cyclic washing unit, then colored particles flow from the pigmented fabrics to the white fabrics and discolor them.
To avoid such discoloration of the white wash, the colored materials have hitherto been washed either in a separate machine or in a bath-change washing stretch which does not work by counterflow. This means higher investment costs, since the bath-change washing stretch is considerably more expensive than a counterflow washing machine and it means higher wash costs. The use of this unit costs considerably more than does that of the counterflow washing machine.
If on account of these disadvantages one nevertheless directly washes the colored laundry in a counterflow wash channel, then the bulk of the wash chambers must be left empty so that the staining of a subsequent white wash will be prevented. With strongly colored materials 60-70% of the washing machine should be left empty. Because of that the performance of the machine is considerably reduced, although on the other hand the machine usage cannot be reduced economically because water, steam and washing liquors must be supplied in the same amounts even when there is no wash in some of the chambers.
In order to eliminate these empty chambers and the difficulties involved in their use, as taught by German Patent DE-OS No. 29 49 228, the liquid counterflow can be bypassed around the wash chamber in which one finds a colored batch of wash by a plurality of valves and shunt pipes. This also in principle maintains the counterflow except for the selected wash chamber filled with colored wash. However an expensive and cumbersome control apparatus is required for this system.